James Cutfield, 51, was the head of crew aboard the 56-meter (184-foot) sailing boat when it capsized in the throes of a ferocious storm last Monday, killing six passengers, including British tycoon Mike Lynch and his 18-year-old daughter, Hannah. The yacht's chef Recaldo Thomas also likely died in the wreck.
The other victims were Morgan Stanley International director Jonathan Bloomer, prominent American lawyer Chris Morvillo, and both of their wives - Judy Bloomer and Neda Morvillo. Chris Morvillo, a partner at Clifford Chance, was involved in successfully defeating the US fraud case against Lynch in June.
RELATED: Here's what we know about why a luxury sailing boat sank off the coast of Sicily
Cutfield and 14 other people survived the sinking, including Lynch's wife, Angela Bacares.
A weather phenomenon known as a waterspout - one of several types of tornadoes - is thought to have capsized the yacht. But Italian authorities are investigating whether the crew's actions and their handling of the boat contributed to the deadly sinking.
New-Zealand born Cutfield is not in custody, according to Italian prosecutors, but he cannot leave the country while the investigation is ongoing.
Those killed were likely asleep at the time of the storm, a prosecutor said at the weekend, which is why they were unable to escape. On Saturday, the prosecutor and head of the fire brigade recovery team both said five bodies were found in the same room of the ship, which may have meant they were searching for an air pocket while the ship sank.
RELATED: Last body from sunken superyacht has been found off Sicily, Italian Coast Guard says
Rescuers locate body of last missing person in superyacht sinking
Investigators warned that the circumstances of the sinking remain largely unclear, including whether there was a black box onboard the ship, and if some of the ship's hatches were left ajar - which would explain why it sank so rapidly.
Salvage crews are expected to raise the Bayesian - named after the statistical theory on which Lynch made his fortune - in the coming weeks. Under Italian law, the cost of raising and salvaging the ship falls on the ship's owner.
As Bacares' company owns the vessel, they must find a salvage company and raise the ship, which is then handed to Italian authorities as part of the investigation, the main prosecutor Ambrogio Cartosio said on Saturday.
After the yacht is raised, investigators will determine if the hatches were open during the storm, Cartosio added.
Italian prosecutors will also investigate whether the ship's chief mate was on the bridge when the ship sunk, and if anyone tried to warn the passengers of imminent danger.